Thermoplastic polymers are commonly used to manufacture various shaped articles that may be use in applications such as automotive parts, food containers, electrical parts, etc. Shaped articles comprising polyester may be prepared from the molten polymer by a number of melt extrusion processes such as injection molding, compression molding, and blow molding.
Poly(trimethylene) terephthalate (PTT), produced from renewable source of 1,3-propanediol and developed by E. I. du Pont de Nemours & Company (DuPont), is commercially available under Sorona® resin. DuPont pioneered a way to produce the 1,3-propanediol from renewable resources including corn sugar. Sorona® resin has properties including semi-crystalline molecular structure.
It is desirable to develop a thermoplastic polyester composition such as PTT that can be crystallized rapidly from the melt, in order to improve the injection molding processing, and at the same time, improve the hydrolytic stability of the thermoplastic composition.
To increase the crystallization rate of the PTT molding resins, and thus reduce the cycle time of thermoplastic molding processes, nucleating agents usually are added in order to increase the rate of crystallization. Ionomers, which can often act as nucleating agents in polyesters, do not always give desirable results for PTT. Furthermore, other additives, for instance, the reactive polymer tougheners can have unexpected and deleterious affects on the rate of crystallization of PTT.
Needed are processes for preparing compositions that exhibit a combination of performance properties including rapid crystallization, excellent hydrolysis resistance, and high Notched Izod impact resistance in a toughened PTT composition.